Alpha-emitting radionuclides are good potential candidates for radioimmunotherapy. 225Ac decays through a chain of 3 alpha emissions to 213Bi.
As described by Davis, I. A. et al in the article “Comparison of Actinium 225 Chelates: Tissue Distribution and Radiotoxicity” published in Nucl. Med. Biol., Vol. 26, pp 581–589, 1999; by Deal, K. A. et al. in the article “Improved in Vivo stability of Actinium-225 Macrocyclic Complexes” published in J. Med. Chem., Vol. 42, pp. 2988–2992, 1999 and by Grote Gansey, M. H. B. et al. in the article “Conjugation, Immunoreactivity, and Immunogenicity of Calix (4) arenes; Model Study to Potential Calix (4) arenes—Based Ac3+Chelators” published in Bioconj. Chem., Vol.10, pp 610–623, 1999, the stability of bifunctional chelating agent of actinides, lanthanides and bismuth is not satisfactory.
An object of the invention is to provide more effective bifunctional chelating agents for metals especially actinides and lanthanides and bismuth.